Arginine side chain assignments in uniformly N-15-labeled proteins using the novel 2D HE(NE)HGHH experiment

A novel 2D NMR experiment, 2D HE(NE)HGHH, is presented for the assignment of arginine side chain H-1 and N-15 resonances in uniformly N-15-labeled proteins. Correlations between H-1(epsilon), H-1(gamma) and H-1(eta) are established on the basis of (3)J(N-15,H-1) heteronuclear scalar coupling constants, and sequence-specific assignments are obtained by overlap of these fragments with H-1(gamma) chemical shifts obtained by assignment procedures starting from the polypeptide backbone. Since guanidino protons exchange quite rapidly with the bulk water, the 2D HE(NE)HGHH pulse scheme has been optimized to avoid saturation and dephasing of the water magnetization during the course of the experiment. As an illustration, arginine side chain assignments are presented for two uniformly N-15-labeled proteins of 7 and 23 kDa molecular weight.